Sodium dichloro s-triazine trione (herein at times called "SDT") has been heretofore manufactured by chlorinating disodium cyanurate and then reacting the resulting dichlorocyanuric acid with sodium hydroxide, e.g. as described in U.S. Pat. No. 3,294,797 issued Dec. 27, 1966 to C. D. Shallenberger et al. However, that preparation of SDT has the disadvantage of producing an aqueous sodium chloride waste stream of substantial size from the disodium cyanurate chlorination step.
It has also been known that salts of dichlorocyanuric acid can be prepared by chlorinating cyanuric acid in the presence of the hydroxide of the desired metal, e.g. as described in U.S. Pat. No. 3,336,228 issued Aug. 15, 1967 to R. J. Fuchs et al.
More recently, it has been found that useful compositions containing SDT and byproduct sodium chloride can be prepared in high yields with essentially no waste disposal requirements by chlorinating a sodium s-triazine trione in an aqueous slurry and then converting the slurry to a solid composition by water removal (e.g. spray drying) as described in U.S. Pat. No. 4,122,267 issued Oct. 24, 1978 to G. D. Nelson et al. Although the discovery was a significant advance in the art, difficulties have been experienced at times in handling the reaction slurry, e.g. line plugging and undesirably long reaction times. In addition, because the chlorination is exothermic, a refrigeration system is generally required to maintain the reaction temperature of 10.degree.-60.degree. C. (preferably 40.degree.-45.degree. C.) prescribed in that patent. It would be less costly to carry out the reaction without such refrigeration, but it has been expected that a higher reaction temperature would result in formation of substantial quantities of nitrogen trichloride, a byproduct which is toxic and highly explosive. See U.S. Pat. No. 3,178,429 issued Apr. 13, 1965 to S. Vazopolos.
An improved process by which such SDT compositions can be prepared in high yields with essentially no waste disposal requirements is very desirable, and it is an object of this invention to provide such a process. Another object is such a process which does not require use of a refrigeration system. Another object is such a process in which the reaction mixture is subject to more convenient handling and control. A further object is such a process having a relatively short reaction time. An important object is such a process which does not result in formation of NCl.sub.3 in amounts too large for non-hazardous disposal. Still another object is to provide SDT-containing compositions prepared in accordance with such a process. These and other objects of the invention will be more fully apparent from the following detailed disclosure, in which all parts and percentages are by weight and all temperatures are in degrees Centrigrade except where otherwise noted.